This invention relates to a novel class of heterocyclic compounds useful for selectively inhibiting elastase, selectively inhibiting chymotrypsin-like enzymes, selectively inhibiting trypsin-like enzymes, or for generally inhibiting serine proteases of all classes. Certain clinical symptoms found in pancreatitis, emphysema, rheumatoid arthritis, inflammation, and adult respiratory distress syndrome are believed to be caused by uncontrolled elastase in the affected tissues. Likewise, similar clinical symptoms found in the same diseases are believed to be caused by uncontrolled cathepsin G, mast cell chymase, and other chymotrypsin-like enzymes. In vitro, proteolysis by serine proteases of the elastase, chymotrypsin, and trypsin families is often a severe problem in the production, isolation, purification, transport and storage of valuable peptides and proteins.
It is an object of this invention to find a novel group of specific inhibitors for elastase, chymotrypsin, trypsin, and other serine proteases of similar substrate specificity, and serine proteases in general. Inhibitors are substances which reduce or eliminate the catalytic activity of enzymes. Chymotrypsin and chymotrypsin-like enzymes normally cleave peptide bonds in proteins and peptides where the amino acid residue on the carbonyl side of the split bond (P.sub.1 residue) is typically Trp, Tyr, Phe, Met, Leu or other amino acid residues which contain aromatic or large alkyl side chains. Elastase and elastase-like enzymes, on the other hand, cleave peptide bonds where the P.sub.1 amino acid residue is much smaller, typically Ala, Val, Ser, Leu and other similar amino acids. Trypsin-like enzymes hydrolyze peptide bonds where the P.sub.1 amino acid is Lys or Arg. All of the above enzymes have extensive secondary specificity and recognize amino acid residues removed from the P.sub.1 residue. The inhibitors of this invention would be useful for treating diseases such as pancreatitis, emphysema, rheumatoid arthritis, adult respiratory distress syndrome, and inflammatory diseases which involve destruction of tissue by serine proteases. In some cases, it would be more useful to utilize a specific elastase, trypsin or chymotrypsin-like enzyme inhibitor, while in other cases an inhibitor with broader specificity would be appropriate.
It is an object of this invention to find a novel group of specific inhibitors useful in vitro for inhibiting elastase, trypsin, chymotrypsin and other serine proteases of similar specificity, and for inhibiting serine proteases in general. Such inhibitors could be used to identify new proteolytic enzymes encountered in research. They could also be used in research and industrially to prevent undesired proteolysis that occurs during the production, isolation, purification, transport and storage of valuable peptides and proteins. Such proteolysis often destroys or alters the activity and/or function of the peptides and proteins. Uses would include the addition of the inhibitors to antibodies, enzymes, plasma proteins, tissue extracts, or other proteins which are widely sold for use in clinical analysis, biomedical research, and for many other reasons. For some uses a specific inhibitors would be desirable, while in other cases, an inhibitor with general specificity would be preferred.